For effective bleaching with hydrogen peroxide, the latter must be converted into a species having more bleaching activity. One possibility for generating activated peroxy compounds is the use of peracid precursors, so-called “bleach activators” such as TAED, that are converted by perhydrolysis into the active species.
A further possibility for generating activated species is enzymatically catalyzed perhydrolysis of carboxylic acid esters or nitrile compounds using perhydrolases.
Lastly, it is also known to use bleach catalysts to generate activated species, a “bleach catalyst” being understood as a substance that can improve the bleaching performance of hydrogen peroxide on a bleachable material without itself participating stoichiometrically in the reaction.
The use of bleach catalysts has the advantage, as compared with the other bleach activation methods, that substoichiometric quantities of the compound are sufficient, with the result that space and weight can be saved in the formulation of the bleach-containing product. In addition, the reduction in weight, especially in the context of washing and cleaning applications, is also associated with the advantage that less material is discharged into the environment, which is particularly advantageous for ecological reasons. Transportation and packaging costs can also be reduced as a result.
Consideration must also be given to the fact that premature hydrolysis can occur when bleach activators such as nitrites or TAED are used in the presence of water, whereas this problem can be very largely eliminated with the use of bleach catalysts. Furthermore, the production of acids that occurs in the context of noncatalytic bleach activation based on peracids causes a shift in pH that can have an unfavorable effect on bleaching performance. In addition, the bleaching performance of most bleach activators at low temperatures is often unsatisfactory.
For the reasons cited above, the use of bleach catalysts is of particular interest as compared with the other techniques for bleach activation, so that a demand exists in principle for novel bleach catalysts.
Bleach catalysts that have been described are, in particular, metal complexes of organic ligands such as salenes, saidimines, tris[salicylideneaminoethyl]amines, monocyclic polyazaalkanes, cross-bridged polycyclic polyazaalkanes, terpyridines, and tetraamido ligands. A disadvantage of the metal complexes just described is, however, they either they do not possess sufficient bleaching performance especially at low temperature, or that, with sufficient bleaching performance, undesirable damage occurs to colors and, in some cases, also to textile fibers.
Some of the tris(heterocyclyl) ligands and metal ligand complexes usable according to the present invention are already known in the existing art. For example, Brown et al. (J. Am. Chem. Soc. 103 (1981) 6953-6959) and Kimblin et al. (J. Chem. Soc., Chem. Commun. (1995) 1813-1815) describe tris(imidazolyl)phosphines and -carbinols and their use, in particular in complex with zinc(II), as a model for the active center of the enzyme carbonic anhydrase. Ruther et al. (J. Chem. Soc., Dalton Trans. (2002) 4684-4693) describe chromium(III) and vanadium(III) complexes of tris(imidazolyl)phosphines and -alkanes and their use to catalyze the reaction of ethylene to 1-alkenes or polymers. Brown et al. (Inorganica Chimica Acta 108 (1985) 201-207) describe Co(II) complexes, and Schiller et al. (Inorg. Chem. 44 (2005) 6482-6492) describe Cu(II) complexes, of tris(imidazolyl)phosphines and their use for catalyzing the hydrolysis of phosphate esters. Allen et al. (Inorg. Chem. 36 (1997) 1732-1734) describe copper(II) complexes, and Vankai et al. (Inorg. Chem. 31 (1992) 343-345) describe iron(II)/(III) complexes, of tris(imidazolyl)phosphines and their use to hydroxylate alkanes. Sorrell et al. (Inorg. Chem. 34 (1995) 952-960) describe copper(I) complexes of tris(imidazolyl)phosphines and their use as a model for the active center of copper-containing enzymes. Wu et al. (Inorg. Chem. 29 (1990) 5174-5183) describe iron(III) and manganese(III) complexes of tris(imidazolyl)phosphines. Kurtz (Chem. Rev. 90 (1990) 585-606) describes iron complexes of tris(imidazolyl)phosphines and their structural characterization. Enders et al. (Z. Anorg. Allg. Chem. 630 (2004) 1501-1506) describe lithium, copper, silver, and scandium complexes of tris(imidazolyl)phosphines.
Byers et al. (J. Organometallic Chemistry 385 (1990) 417-427; J. Chem. Soc., Chem. Commun. (1988) 639-641) describe methane trisubstituted with heterocycles, as well as Pd(II) complexes of those ligands. Sorrell et al. (J. Am. Chem. Soc. 109 (1987) 4255-4260) describe a complex of Cu(I) and methoxymethane trisubstituted with imidazole derivatives, as a model of hemocyanin.
Keene et al. (Inorganica Chimica Acta 187 (1991) 217-220; Inorg. Chem. 27 (1988) 2040-2045) describe central atoms trisubstituted with pyridine, as well as Ru(II) complexes of those ligands. Kuo et al. (J. Organometallic Chemistry 588 (1999) 260-267) describe complexes of tris(2-pyridyl)phosphines and transition metals of the sixth group of the periodic table, as well as a structural investigation thereof. Anderson et al. (J. Chem. Soc., Dalton Trans. (2000) 3505-3512) describe phosphine oxide and methane trisubstituted with heterocycles, as well as iron complexes of those ligands. Adam et al. (J. Chem. Soc., Dalton Trans. (1997) 519-530) describe cobalt complexes of tris(2-pyridyl)methane and tris(2-pyridyl)phosphine. Astley et al. (J. Chem. Soc., Dalton Trans. (1996) 1845-1851) describe central atoms trisubstituted with pyridine, as well as nickel and zinc complexes of those ligands. Kurtev et al. (J. Chem. Soc., Dalton Trans. (1980) 55-57) describe Ru(II) and Rh(I) complexes of tris(2-pyridyl)phosphine and use of the rhodium complexes for hydroformylation reactions. Astley et al. (J. Chem. Soc. Dalton Trans. (1995) 3809-3818) describe copper and zinc complexes of tris(2-pyridyl)phosphines.
WO 2004/014052 discloses central atoms trisubstituted with heterocycles, as well as metal complexes of those ligands with metals of groups 3, 4, 5, or 6 of the periodic table, and the use of said metal complexes as polymerization catalysts.
The use of tris(heterocyclyl)-metal complexes as bleach catalysts is already disclosed, for example, in DE10163331, DE19713851, and JP08300624. Here, however, the heterocycles are bound to the central atom of the ligand not directly, but instead via an alkylene bridge. It has been found, however, to be particularly advantageous that the heterocycles are bound directly to the central atom of the ligand, without an intermediate bridge.